Trimmer tab control for airplanes



July 10, 1945. I J MARTIN TRIMMER TAB CONTROL FOR AIRPLANES Filed 'Mafch 9, 1942 2 Sheets-Sheet 1 July 10, 1945. J. MARTIN v TRIMMER TAB CONTROL FOR AIRPLANES Filed March 9, 1942 2 Sheets-Sheet 2 Patented July 10, 1945 i 1 UNITED STAT Es PATEN OFFICE: Y t TRIMMER TABCONTROLFOR AIRPLANES,

James Martin, HigherDenham near Uxbridge,

. England] n j.

Application March- 9, 1942, Serial No. 434,013 i In Great Britain March 15,1941

This invention relates to the adjustment and mounting of trimmer tabs on elevators, ailerons,

rudders or other control members of airplanes,

and has for'its chief object to enable .fine and positive adjustments of a trimmer tab relatively to its/elevator Or -other appropriate airplane part to be effected from a conveniently accessible point. Another object of this invention is to obviate extraneous fitments for the setting and looking of the trimmer tabs and also to isolate sub-. stantially the whole of the adjusting. and locking means from a trimmer tab in such manner that there is the mim'mum gap between the trimmer tab and elevator or equivalent member and no projecting parts affecting the streamline continuity of the tab and elevator or equivalent memher. A still further object of this inventionis to support the adjusting andlocking means by parts of the aircraft which will ensure a firm mounting and the minimum of vibrational and other shocks liable to upset the trimming or to produce looseness in the elements of the adjusting means.

In carrying one form of this invention into practice as applied to a trimmer tab on an elevator, the tab is suitably journalled at its leading edge across side ribs of the elevator and at one end has fixed to it a lever projectingforwardly into the elevator andconnected by a link to a lever supported for oscillation within'the elevator in juxtaposition to the trailing end opening in the elevator which receives the tab. This latter lever is connected in turn by a longitudinal push rod to a, screw jack, the appropriate rotary threaded element of which is driven from a spindle mounted in bearings in diametrically opposed parts of a main supporting sleeve, bush or shaft of the elevator, suitable universal joints being provided with the spindle to compensate for changes effected in the direction of the axis of the push rod and jack and also to enable the spindle to be driven by a tool inserted through an opening in the leading edge of the elevator. A similar arrangement may be employed with a trimmingtab mounted in a rudder or other control member "of an airplane.

. jack manipulating. and adjusting means .fortthe wtrimmertab. i i H Fig. 3is a broken plan view of Fig. 2. j i Referring to thedrawings'the skin or outline-of the elevatorisindicated by the broken lines Land the: inner andouterribs 2 and 3 respectively. of i one side of the elevator arelikewise shown in broken lines, these being made use of in the mounting of the trimming mechanism. The shaft carrying the elevatorishown broken in Figs. 2 and 3) is indicated by the reference numeral 4 and the trimmer tab by the reference numeral 5.

The trimmer tab 5 is a close fitin theopening 6 in the trailing endof the elevator and fixed to one of its side edges close to its leading edge is a forwardly directed arm 1 forming a lever by which the trimmer tab is adjusted about the axis of a pair of lateral spigots 8 fixed to the tab and supported in ballorother bearingsQ carried by the trailing ends of the rib 2. The arm"! canbe an integral part of oneofthe plates 10 riveted to the trimmer tab and carrying the spigots 8.

The arm I projects forwardly into the elevator and passes through a narrow slot in the transverse or stepped part 2a. of the rib 2 form! ing a front corner of the opening. '6 so that the arm 1 does not project above or below the skin of the elevator. Leverage is imparted to the arm 1 to angularly adjust the trimmer tab from a remote control device'situated at the forward end of the elevator, and the appropriate connection to this remote control device is by means of a link ll connecting the free end of the arm I to the free end of alever [2 receiving one end l3forms part of a screwjack, forwhichpurpose it is formed with an internally threaded sleeve 1'! into which is threaded a screw threaded shaft l8 adapted to be rotated to apply fore and aft traverse to the push rod l3. The three pivots of the connections of the arm I link II and lever [2 provide a triangulated. arrangement (see Fig. 2) which with the pushrod l3 affords an automatic locking of the trimmer tab in any of its positions of adjustment.

The means for rotating the screw l8, and comprising the said remote control' device, comprises a spindle) firmly mounted for rotation in bearing bushes 2|] fixed in a pair of diametrically opposed bosses 2| integral with the sleeve 22 fixed across the ribs 2 and 3 the beforesaid shaft 4'.

and mounted upon The connection of the screw ill to the spindle I9 is by means of a universal joint 23, and a similar joint 24 is fitted to the front end of such spindle to enable the spindle to be driven by a key or crank inserted at a convenient angle through an opening in an accessible part of the leading end of the elevator, the front element of the universal joint 24 being adapted to receive the key or crank. Or, alternatively, the said front element can receive a sprocket or flexible shaft or be otherwise adapted for operation from a remote control such as e. g. trimmer tab adjusting means close to the pilots seat.

Access to the pivots of the link II and lever l2 can be effected through an opening 25 in the rib 3, the pivotal joints preferably being screws 26 threaded at one end into'bosses 21 formed in the appropriate parts of the link, lever and push rod, the latter having a bifurcated head joint 24 and journalled in the leading edge of the elevator. The forward end of the shaft being shaped for engagement by an operating key or shaft.

I claim:

In an airfoil, the combination of, an aileron, a trimmer tab pivotally mounted on the trailing edge of said aileron, a horn centrally disposed on and rigidly fixed to the forward part of the trimmer tab and projecting forwardly through aslot into the trailing edge of said aileron, a

link having one end pivotally mounted to the end of said projecting part of said horn, asecand link positioned inside the trailing edge of said aileron and having one end pivotally mounted therein, a screw-threaded jack positioned inside said aileron having an elongated shaft extending rearwardly inside the trailing edge of said aileron, the other ends of said links being pivotally connected to said shaft at a common oint to give a triangulated disposition of the pivot-s which furnishes spacial rigidity, positive control of the trimmer tab, and divides the force applied to said shaft by the trimmertab.

JAMES MARTIN; 

